This Civil War-era cannonball was found on Governor's Island. Photo: Govislandblog.com

Talk about a possible “boom” for tourism!

A Civil War-era cannonball was discovered today near the ferry landing on Governors Island, authorities said.

The 350-pound, 20-inch round projectile was found around 8:50 a.m. by workers doing construction near Soissons Dock, the main access point for the island, said Elizabeth Rapuano, a spokeswoman for the city-run Trust for Governors Island.

“They were digging in the water with a backhoe, removing muck and mud, when this thing dropped out of the bucket” said one police source.

Cops cordoned off the area and re-directed students who attend the New York Harbor School, said DOE spokeswoman Margie Feinberg.

The NYPD Bomb Squad and Emergency Service Unit were dispatched to the island to inspect the antiquated device. It was eventually deemed safe and removed to another part of the island for further examination.

The island served as a strategic military stronghold until it was overrun by British troops in August 1776.

The island was later returned to New York State and, prior to the War of 1812, the US Army constructed Fort Jay and Castle Williams.

Today, 150 acres are owned by the city, while a separate 22 acres are managed by the National Park Service.